Morphologic characterization of early prostatic carcinomas in the ACI rat: a light and electron microscopic study.

The ACI rat constitutes a unique model for human prostatic carcinogenesis. A high percentage of these animals spontaneously develop prostatic carcinomas in the ventral lobe as they age. The light microscopic appearance of these tumors is similar to the cribriform pattern of adenocarcinoma in human prostate. In order to further characterize this useful model, we carried out light and electron microscopy studies of the morphology of carcinomatous lesions developing in these animals. Sixteen rats ranging in age from 25 to 43 months were examined histologically, and ultrastructural studies were performed on eight of these cases. The neoplastic cells showed features of well-developed secretory epithelium including prominent Golgi apparatus, abundant rough endoplasmic reticulum, and numerous secretory vacuoles. Microvilli were numerous in some cells and focal apocrine secretory activity was present. Intraluminal crystals similar to those associated with human prostate carcinoma were observed in one of our cases. Prostate carcinomas developing in the ACI rat share many of the ultrastructural features of human prostatic carcinoma.